Further observations on metal-backed patellar component failure.

The clinical data, failure pattern, symptoms, roentgenographic findings, and failure mechanism of a series of 25 metal-backed patellar component failures are summarized. Diagnosis of implant failure was unknown prior to arthrotomy in seven of 25 cases (28%). Clinical findings and history were not helpful in making the diagnosis. Roentgenographic findings led to the diagnosis in 17 of 18 and were by far the most useful data. Metal-backed patellar component failure is a new complication of total knee arthroplasty and will be seen in increasing numbers. Caution is urged in implanting metal-backed designs until further design research is done.